Plants alcohol dehydrogenase

Hanson, A.D., Jacobsen, J.V. Zwar, J.A. (1984). Regulated expression of three alcohol dehydrogenase genes in barley aleurone layers. Plant Physiology, 75, 573-81. 

MARTINEZ, M.C., ACHKOR, H., PERSSON, B., FERNANDEZ, M.R., SHAFQAT, J., FARRES, J., JORNVALL, H., PARES, X., Arabidopsis formaldehyde dehydrogenase. Molecular properties of plant class III alcohol dehydrogenase provide further insights into the origins, structure and function of plant class P and liver class I alcohol dehydrogenases, Eur. J. Biochem., 1996,241, 849-857. 

NADH. The enzymes are widely distributed in nature, being found in microorganisms, plants, and animals. Catalytic mechanism, specificity, and physical properties of the alcohol dehydrogenases have been reviewed in detail (91-93). 

While most alkaloids do not contain aldehydes when they enter mammalian, microbial, or plant tissues, this functional group may become important when formed as a metabolite of alcohols (via alcohol dehydrogenase) or amines (via oxidative dealkylation and oxidative deamination). Aldehyde dehydrogenases catalyze oxidation of aldehydes to the corresponding carboxylic acids. The physical properties, catalytic mechanism, and specificity of this group of enzymes has been reviewed (99). The general reaction catalyzed by aldehyde dehydrogenase is seen in Eq. (9). 

Figure 6.1 Pathways involved in glucose oxidation by plant cells (a) glycolysis, (b) Krebs cycle, (c) mitochondrial cytochrome chain. Under anoxic conditions. Reactions 1, 2 and 3 of glycolysis are catalysed by lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase, respectively. ATP and ADP, adenosine tri- and diphosphate NAD and NADHa, oxidized and reduced forms of nicotinamide adenine dinucleotide PGA, phosphoglyceraldehyde PEP, phosphoenolpyruvate Acetyl-CoA, acetyl coenzyme A FP, flavoprotein cyt, cytochrome e, electron. (Modified from Fitter and Hay, 2002). Reprinted with permission from Elsevier...

Alcohols are oxidized to aldehydes by the liver enzyme alcohol dehydrogenase, and aldehydes to carboxylic acids by aldehyde dehydrogenase. In mammals, monooxygenases can be induced by plant secondary metabolites such as a-pinene, caffeine, or isobornyl acetate. Reduction is less common and plays a role with ketones that cannot be further oxidized. Hydrolysis, the degradation of a compound with addition of water, is also less common than oxidation. 

In a recent study (54), we showed increased activities of two enzymes of the general phenylpropanoid pathway, PAL and 4-coumarate CoA lig-ase, as well as one enzyme of the specific pathway of lignin biosynthesis, cinnamy 1-alcohol dehydrogenase (CAD), in resistant plants at the time of the hypersensitive host cell death. On the other hand, decreased activities were observed at the same time with susceptible host plants (54). Furthermore, we showed that the well known increase in peroxidase activities, which is strong in resistant and only weak in susceptible plants (55-58), is at least partly due to the increased activity of the lignin biosynthetic pathway (54,59). 

Pinhero, R. G., Copp, L. J., Amaya, C. -L., Marangoni, A. G., Yada, R. Y. (2007). Roles of Alcohol dehydrogenase. Lactate dehydrogenase and Pyruvate decarboxylase in Low Temperature Sweetening in a tolerant and susceptible varieties of Potato (Solanum tuberosum). Physiologia Plant, 130(2), 230-239. 

The volatiles produced by the LOX pathway and autoxidation are typically volatile aldehydes and alcohols responsible for fresh and green sensorial notes. In the LOX pathway these volatile compounds are produced in response to stress, during ripening or after damage of the plant tissue. The pathway is illustrated in Scheme 7.2. Precursors of the LOX (EC 1.13.11.12) catalysed reactions are Cis-polyunsaturated fatty acids with a (Z,Z)-l,4-pentadiene moiety such as linoleic and a-linolenic acids that are typically oxidised into 9-, 10- or 13-hydro-peroxides depending on the specificity of the LOX catalyst. These compounds are then cleaved by hydroperoxide lyase (HPL) into mainly C, C9 and Cio aldehydes, which can then be reduced into the corresponding alcohols by alcohol dehydrogenase (ADH EC 1.1.1.1) (Scheme 7.2) [21, 22]. The production of volatile compounds by the LOX pathway depends, however, on the plants as they have different sets of enzymes, pH in the cells, fatty acid composition of cell walls, etc. 

Ralph, J., Hatfield, R. D., Piquemal, J., Yahiaoui, N., Pean, M., Lapierre, C., Boudet, A. M., 1998, NMR characterization of altered lignins extracted from tobacco plants down-regulated for lignification enzymes cinnamyl alcohol dehydrogenase and cinnamyl-CoA reductase, Proc. Natl. Acad. Sci. USA 95 12803-12808. 

Halpin, C., Holt, K., Chojecki, J., Oliver, D., Chabbert, B., Monties, B., Edwards, K., Barakate, A., and Foxon, G. A., 1998, Brown-midrib maize (bml) - a mutation affecting the cinnamyl alcohol dehydrogenase gene, Plant J. 14 545-553. 

Sibout, R., Eudes, A., Pollet, B., Goujon, T., Mila, I., Granier, F., Seguin, A., Lapierre, C., and Jouanin, L., 2003, Expression pattern of two paralogs encoding cinnamyl alcohol dehydrogenases in Arabidopsis. Isolation and characterization of the corresponding mutants, Plant Physiol. 132 848-860. 

O Connell, A., Holt, K., Piquemal, J., Grima-Pettenati, J., Boudet, A., Pollet, B., Lapierre, C., Petit-Conil, M., Schuch, W., and Halpin, C. 2002, Improved paper pulp from plants with suppressed cinnamoyl-CoA reductase or cinnamyl alcohol dehydrogenase, Transgen. Res. 11 495-503. 

Mitchell, H.J., Hall, J.L., and Barber, M S., 1994, Elicitor-induced cinnamyl alcohol dehydrogenase activity in lignifying wheat (Triticum aestivum L.) leaves, Plant Physiol. 104 551-556. 

Walter, M.H., Grima-Pettenati, J., Grand, C., Boudet, A.M. Lamb, C.J. (1990). Extensive sequence similarity of the bean CAD4 (cin-namyl-alcohol dehydrogenase) to a maize malic enzyme. Plant Molecular Biology 15, 525-6. 

Christie, P.J., Hahn, M. Walbot, W. (1991). Low temperature accumulation of alcohol dehydrogenase-1 mRNA and protein activity in maize and rice seedlings. Plant Physiology 95, 699-706. 

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